updated info for antigen install option

README.md

@@ -136,9 +136,12 @@ You then need to select this theme in your `~/.zpreztorc`:
 If you prefer [antigen](https://github.com/zsh-users/antigen), just add this
 theme to the antigen config in your `~/.zshrc`:
 
-    $ echo 'antigen theme /vagrant_data powerlevel9k' >> ~/.zshrc
+    $ echo 'antigen theme bhilburn/powerlevel9k powerlevel9k' >> ~/.zshrc
     $ echo 'antigen apply' >> ~/.zshrc
 
+Note that you should define any customizations before calling `antigen theme`
+(i.e. setting the `POWERLEVEL9K_*` variables) in your `.zshrc`.
+
 #### Step 2: Install Powerline Fonts
 Technically, you don't *have* to install Powerline fonts. If you are using
 a font that has some of the basic glyphs we need, you can use the theme in